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1. What is a centrifugal pump? Briefly describe the working principle of centrifugal pump? answer: A pump that uses the centrifugal force generated by the rotation of an impeller to transport liquid is called a centrifugal pump. How it works is: The motor drives the impeller to rotate at high speed, causing the liquid to generate centrifugal force. Due to the centrifugal force, the liquid is thrown into the side channel and discharged out of the pump, or into the next-stage impeller, thereby reducing the pressure at the impeller inlet and forming a pressure difference with the pressure acting on the suction liquid. The pressure difference causes the liquid to be sucked into the pump. Because the centrifugal pump keeps rotating, the liquid is continuously sucked in and discharged. 2. Compared with other types of pumps, what are the advantages and disadvantages of centrifugal pumps? answer: Compared with other types of pumps, centrifugal pumps have a series of advantages such as simple structure, small size, light weight, stable flow, easy manufacturing and easy maintenance. However, centrifugal pumps have poor applicability to high-viscosity liquids, small flow rates, and high pressure situations, and the pump usually needs to be primed before starting. These are its shortcomings. 3. How to classify various types of pumps? Answer: There are several ways to classify various types of pumps:: 1． According to principle: It can be divided into volumetric pumps, vane pumps, injection pumps, etc. Positive displacement pumps are pumps that rely on changes in working chamber volume to transport liquids, such as reciprocating pumps, rotor pumps, and gear pumps. A vane pump is a pump that relies on the rotation of an impeller to transport liquid, such as: Centrifugal pump, axial flow pump, etc. A jet pump relies on the energy of a working fluid to deliver another fluid, e.g.: Jet pump, water pump, etc. 2. According to the prime mover: It can be divided into steam turbine, steam reciprocating pump, electric centrifugal pump and electric reciprocating pump. 3． According to conveying medium: There are water pumps, oil pumps, acid pumps, and alkali pumps. 4． According to the installation position of the shaft: There are vertical pumps and horizontal pumps. 5. According to the temperature of the conveying medium ； There are cold medium pumps and hot medium pumps. 6. According to the impeller stage: There are single-stage pumps, double-stage pumps, and multi-stage pumps. 7. According to impeller feeding mode: There are single suction type and double suction type. 8. According to the joint form of pump shell: There are horizontal center opening type and vertical segmented type. 4. Briefly describe the classification of centrifugal pumps. answer: There are different types of centrifugal pumps according to different usage requirements. According to the number of impellers, it can be divided into single-stage pump and multi-stage pump. ； According to the liquid inlet mode of the impeller, it can be divided into single suction type and double suction type. ； According to the split state of the pump casing, it can be divided into horizontal split pumps and vertical split pumps with the pump shaft. ； According to the structure of the pump casing, it can also be divided into volute pumps and turbine pumps. In addition, according to the size of the pump head, it is divided into low-pressure pumps (head less than 20 meters of water column), medium-pressure pumps (20 to 160 meters of water column) and high-pressure pumps (higher than 160 meters of water column). Different conveying media are divided into clean water pumps, oil pumps and corrosion-resistant pumps. 5. What are the main parameters of a centrifugal pump? answer: The main performance parameters of centrifugal pumps include speed, flow, head, power and efficiency. (1) Speed: That is, the rotation speed of the centrifugal pump impeller, expressed in r/min. (2) Flow: There is a difference between the flow rate of the pump (that is, the effective flow rate) and the theoretical flow rate. Most of them use the volumetric flow rate Q, and the unit is m3/s, m3/min, m3/h or L/s. Sometimes it is also expressed as mass flow rate G, with units of kg/s, kg/min, and t/h. (3) Lift: The head of the pump H---the increment of the total energy per unit weight of liquid flowing through the pump. Or the effective work done by the working element on the unit weight of liquid discharged by the pump (unit is m-liquid column). (4) Power: There are effective power Neff, internal power Ni and shaft power N. The effective power Neff is the energy obtained from the pump by the liquid flowing out of the pump discharge port per unit time. Internal power Ni (or hydraulic power) is the energy given by the work unit per unit time. Shaft power N refers to the work transmitted from the prime mover to the pump main shaft per unit time. When the pump is working, there will inevitably be mechanical friction losses between moving parts, as well as wheel resistance losses. Collectively called mechanical loss power Nmec. Shaft power is equal to the sum of internal power and mechanical loss power. Right now: N= Ni+ Nmec KW (5)Efficiency: Pump efficiency (total efficiency) η position is an indicator of whether the pump is economical, defined as: η= Neff/N, which is the ratio of effective power to shaft power. In addition to the above, another important performance parameter of the centrifugal pump is the allowable suction vacuum degree [Hs] or the allowable cavitation allowance [NPSH] of the pump. The units are expressed in meters---liquid column. 6. What are the main components of a centrifugal pump? Which parts do you think are wearing parts? answer: The main components of a centrifugal pump include: Impeller, sealing ring, suction chamber, pressure chamber, pump shaft, bearings, shaft seal device, etc. Among them, sealing rings, bearings, and shaft seal devices are more susceptible to damage than other components.